While I already have a full caster and full warrior character (in many variants using a ton of soul stones), I made a hybrid caster-warrior template:
A mystic wraith thrower (PVM)
It might not be the most efficient template, but as I simply got bored playing warrior/sampire or mage/caster templates, I made this true hybrid.
Skills:
Spirit speak 60
Necromancy 60
Throwing 120
Tactics 120
Mysticism 120
Focus 120
Anatomy 120
TOTAL 720
Some pros:
Can cast wraith form, curse weapon, evil omen and corpse skin 100% at 60 necro
Can often leech enough mana back, either with weapon or spell, at 60 spirit speak (even without HML on weapon) to chain AI or recast
Uses the best high-damage weapon in game (soul glaive, which got AI)
Uses the best summon in game (RC) to tank
Reaches max damage modifier cap with 18 lesser slayer soul glaives (all spell channelling or cast enchant)
Reaches max damage increase cap (120 anatomy/tactics)
Uses mysticism spells with super slayer spellbooks for area of effect damage (nether blast, nether cyclone, hail storm)
Uses healing stone for mini heals and emergency cures and heals
Uses curse weapon for big or constant heals
Can debuff (and cure) with cleansing winds
Can leech through most poison with curse weapon
Recalls in wraith form for transportation (100% success chances)
Uses a spell-channelling dispel weapon to dispel (can alternatively use the spell enchant to add "hit spell dispel" to equipped soul glaive)
Can also equip melee weapon with 100% HML/HLL (soul glaives are capped at 50%) in combination with the mystic weapon mastery (cannot do weapon specials though)
Can make any weapon spell channelling with enchant (provided it does not have a hit spell mod already)
Uses mass sleep instead of invisibility to de-aggro mobs
Low maintenance costs (100% LRC suit, no arrows or bandaids ever needed, not much repair needed as a ranged fighter)
Does not rely on chivalry and can therefore drop karma
Does not need elemental damage weapons as it relies on chaining AI and area of effect (mostly chaos) spells
Makes efficient use of follower slots and form on foot (wraith form and RC at 5 follower slots)
Some cons:
Difficult to reach the 1.25 swing speed cap, I am at about 1.75 and find this is enough
Does not do well in settings with lots of minor spawn (e.g. champs) due to no whirlwind (the area of effect weapon for throwing just sucks and killing massive waves of small mobs with area of effect damage spells takes forever)
Does not do well on mobs without lesser slayer vulnerability
Does not do well on mobs with low or no mana
Does not get special move mana reduction from certain skill combos (bushido, parrying, etc.)
Have to constantly cast curse weapon and enchant (if no spell channeling weapon)
Is on foot and thus very slow. Can reach mount speed with gargoyle racial ability flying, but then cannot mana leech enough to chain AI
High insurance costs if you decide to always carry all 18 lesser slayers soul glaives in your bag
High imbuing costs if you decide to get all 18 lesser slayers
Cannot combine RC (causing physicals damage) and corpse skin (raising physical resist)
As mentioned above, my mage/caster or sampire/paladin templates outperform this template, but just in case you get bored to always play minor variants of existing templates: this one makes use of a lot of spells, skill combos (no bushido, no chivalry), items (healing stone) and masteries you generally do not use on a warrior.